CO(2) inhalation as a treatment for apnea of prematurity: a randomized double-blind controlled trial.

Objective: To compare the effect of prolonged inhalation of a low concentration of CO(2) with theophylline for the treatment of apnea of prematurity.

Study Design: Prospective, randomized, double-blind controlled trial of 87 preterm infants with apnea of prematurity (27-32 weeks' gestational age) assigned to either theophylline plus 0.5 L/min of room air via nasal prongs or placebo plus 0.

A randomized controlled trial of theophylline versus CO2 inhalation for treating apnea of prematurity.

Objective: To determine whether inhalation of 0.8% CO(2) in preterm infants decreases the duration and rate of apnea as effectively as or better than theophylline with fewer adverse side effects.

Study Design: A prospective, randomized, control study of 42 preterm infants of gestational age 27 to 32 weeks assigned to receive inhaled CO(2) (n = 21) or theophylline (n = 21).

Measurement of the CO2 apneic threshold in newborn infants: possible relevance for periodic breathing and apnea.

We measured the PCO2 apneic threshold in preterm and term infants. We hypothesized that, compared with adult subjects, the PCO2 apneic threshold in neonates is very close to the eupneic PCO2, likely facilitating the appearance of periodic breathing and apnea. In contrast with adults, who need to be artificially hyperventilated to switch from regular to periodic breathing, neonates do this spontaneously.

Increased peripheral chemoreceptor activity may be critical in destabilizing breathing in neonates.

Periodic breathing and apnea are common in neonates, yet the physiological mechanisms involved are not clear. A low arterial PO2 might magnify peripheral chemoreceptor contribution to breathing, with its baseline variability inducing major changes in ventilation, leading to instability of the respiratory control system. We hypothesized that neonates: (1) would depend much more on the peripheral chemoreceptor contribution to breathing than adult subjects and (2) their baseline arterial PO2 would sit on the steep portion of the ventilation/arterial PO2 relationship on the adult nomogram, making breathing prone to oscillate.

Prostaglandins are responsible for the inhibition of breathing observed with a placental extract in fetal sheep.

We have previously observed that the infusion of a placental extract inhibits breathing movements in fetal sheep, suggesting that a placental factor may be responsible for the inhibition of fetal breathing. Our preliminary results suggested that a small peptide or a substance bound to a peptide was likely responsible for this inhibition. Since prostaglandins are found in high concentrations in the placenta, it is possible that they may be responsible for the inhibition of breathing observed with the placental extract.

Periodicity, mixed-mode oscillations, and quasiperiodicity in a rhythm-generating neural network.

We studied patterns of oscillatory neural activity in the network that generates respiratory rhythm in mammals. When isolated in vitro, this network spontaneously generates an inspiratory-related motor rhythm, with stable amplitude from cycle to cycle. We show that progressively elevating neuronal excitability in vitro causes periodic modulation of this inspiratory rhythm, evoking (in order): mixed-mode oscillations, quasiperiodicity, and ultimately disorganized aperiodic activity.